A large class of machine tools are disposed on a frame which includes a horizontal bed and at least one vertical upright which is mounted on the bed. Depending on the particular construction of the machine tools there are provided on the vertical uprights and on the bed clamping means, and drive means for workpiece and tools, and these are disposed in operable association over three or more axis.
It is known to produce the frame from cast iron or cast steel. The production of these frames is inefficient, since after the casting a further operation such as milling or grinding is necessary. In particular because of this secondary operation it becomes impossible, as a rule, to cast frames for large machine tools in a single casting. A further substantial assembly operation expense is therefor necessary in order to join together these individual pieces.
It is further known to produce a frame of sintered steel. Here also substantial production and assembly expenditures are necessary.
Finally, it is known (for example, see EP 0 046 272 A2), to cast the frame in a single piece using a castable concrete comprising mineral particles bound by a setting polymer resin. This method of manufacture is economical. These frames are characterized by a substantially higher vibration dampening characteristic as compared with the above-mentioned frames constructed of cast iron, cast steel and sintered steel.
It is a common feature of all these known frames, that the uprights which are mounted on the frame project tower-like clear from the bed. Higher loads, inaccuracies in the calibrated assembly of the bed, temperature fluctuations and temperature gradients can therefor result in bending and torsional movement of the upright with respect to the bed. Such movements directly compromise the targeted machine tool precision. In order to improve the precision and minimize the deformation movement of the stand and the bed, the dimensions and the cross-sections of the frame are enlarged. A small improvement in precision is attained at the expense of a substantial increase in the weight and in the material cost of the frame.
The present invention is concerned with the problem of providing a frame for machine tools, which with less expenditure makes possible a higher degree of mechanical precision of the machine tools.